The safety of the human consumer is taken into account during the licensing of veterinary medicines for farm animals.
The routine use of antibiotics and other medicines in farm animals is no longer generally accepted. It may leave significant levels of these medicines in the final product and the environment. Furthermore, the widespread use of some drugs carries the potential to accelerate the development of antibiotic-resistant strains of bacteria. However, farm animal disease cannot yet be completely eliminated by vaccination, biosecurity, improvements in animal care and nutrition and the trend toward extensive and organic farming. Some medicines will continue to be used within all systems of animal production, which is in the interest of animal welfare.
Under European Union (EU) Council Regulation 2377/90/EC Maximum Residue Limits (MRL) in foods of animal origin are set for each farm animal medicine. Pharmacological data are submitted to the licensing authority for veterinary medicines. (In the UK, this is the Veterinary Products Committee of the Veterinary Medicines Directorate. The EU-wide licensing authority is the European Medicines Evaluation Agency). In addition to quantifying a drug’s safety and efficacy in animals, the data also include an assessment of its safety in humans; the license application dossier includes experimental evidence for two key safety criteria, the NOEL and ADI:
- NOEL: The drug’s maximum No Observed Effects Level in humans
- ADI: The Acceptable Daily Intake by mouth of the drug throughout a human lifetime
- MRL: These two parameters are used to set a Maximum Residue Limit for the drug in foodstuffs of animal origin. Levels above this will render the food product unacceptable for the purposes of trade*.
The MRL is used in turn to calculate the minimum withdrawal time needed between the last animal treatment, and slaughter or resumption of egg or milk production, for the animal to have excreted enough of the drug to a point where concentrations in its tissues, eggs or milk fall below the MRL. Animal welfare should not be affected by with-holding medicines at this time; for obvious public health reason, under food hygiene regulations only healthy animals are eligible for meat or milk production.
Withdrawal times for licensed veterinary medicines prior to slaughter, egg or milk production are available on the National Office of Animal Health website. Council Directive 2001/82/EC and the UK's Veterinary Medicines Regulations require that medicines given to food-producing animals are administered according to the licensed dosing regimen for the drug and species of animal; and treatments must be recorded in the farm's medicines register. Other treatments and regimens may be authorised by a veterinary surgeon, but additional restrictions on meat, egg and milk production will apply, such as an increased drug withdrawal time, and in some cases, products are excluded from the human food chain.
(*A safety factor is included at each stage of the calculation. Occasional levels of licensed veterinary medicines in food even considerably above the MRL are unlikely to pose a health threat to the individual consumer).
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